[Simple measuring method for the calculation of the biomechanical forces of the neck muscles].
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Anthropometry↗
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Neck muscle responses to stimulation of monkey superior colliculus. II. Gaze shift initiation and volitional head movements.
We report neck muscle activity and head movements evoked by electrical stimulation of the superior colliculus (SC) in head-unrestrained monkeys. Recording neck electromyography (EMG) circumvents complications arising from the head's inertia and the kinetics of muscle force generation and allows precise assessment of the neuromuscular drive to the head plant. This study served two main purposes. First, we sought to test the predictions made in the companion paper of a parallel drive from the SC onto neck muscles. Low-current, long-duration stimulation evoked both neck EMG responses and head movements either without or prior to gaze shifts, testifying to a SC drive to neck muscles that is independent of gaze-shift initiation. However, gaze-shift initiation was linked to a transient additional EMG response and head acceleration, confirming the presence of a SC drive to neck muscles that is dependent on gaze-shift initiation. We forward a conceptual neural architecture and suggest that this parallel drive provides the oculomotor system with the flexibility to orient the eyes and head independently or together, depending on the behavioral context. Second, we compared the EMG responses evoked by SC stimulation to those that accompanied volitional head movements. We found characteristic features in the underlying pattern of evoked neck EMG that were not observed during volitional head movements in spite of the seemingly natural kinematics of evoked head movements. These features included reciprocal patterning of EMG activity on the agonist and antagonist muscles during stimulation, a poststimulation increase in the activity of antagonist muscles, and synchronously evoked responses on agonist and antagonist muscles regardless of initial horizontal head position. These results demonstrate that the electrically evoked SC drive to the head cannot be considered as a neural replicate of the SC drive during volitional head movements and place important new constraints on the interpretation of electrically evoked head movements.
Animals↗
[Influence of the neck muscles deafferentation on the natural head-forelimb coordination in dogs].
We studied the influence of the neck muscles deafferentation on the natural head-forelimb coordination. This coordination exists in intact dogs at the early stage of acquisition of the instrumental feeding reaction of tonic forelimb flexion aimed at holding a cup with meat during eating when the head is bent down to foodwell. In untrained dogs, the forelimb flexion is preceded by lifting the head bent down to the food; the following lowering of the head leads to extension of the flexed forelimb. For performing the instrumental reaction, the innate coordination has to be rearranged into the opposite one. It is achieved only by learning. It was shown that deafferentation of the neck muscles, which leads to a loss of the neck reflex, did not destroy the innate coordination and did not facilitate its rearrangement during the instrumental conditioning.
Animals↗
Variation of neck muscle strength along the human cervical spine.
The aim of this study was to describe and explain the variation of neck muscle strength along the cervical spine. A three-dimensional model of the head-neck complex was developed to test the hypothesis that the moment-generating capacity of the neck musculature is lower in the upper cervical spine than in the lower cervical spine. The model calculations suggest that the neck muscles can protect the lower cervical spine from injury during extension and lateral bending. The maximum flexor moment developed in the lower cervical spine was 2 times higher than that developed in the upper spine. The model also predicted that the neck musculature is 30% stronger in the lower cervical spine during lateral bending. Peak compressive forces (up to 3 times body weight) were higher in the lower cervical spine. These results are consistent with the clinical finding that extension loading of the neck often leads to injuries in the upper cervical spine. Analysis of the model results showed that neck flexor strength was greater in the lower cervical spine because of the relatively large size of the sternocleidomastoid muscle. The hyoid muscles developed significant flexor moments about the joints of the upper cervical spine, as these muscles had relatively large flexor moment arms; however, this effect was offset by the action of the sternocleidomastoid, which exerted a large extensor moment in the upper spine. Lateral bending strength of the neck muscles was governed by geometry (i.e., moment arms) rather than by muscle size.
Journal Article↗
Organization of segmental input from neck muscles to the external cuneate nucleus of the cat.
The musculotopic organisation of projections to the external cuneate nucleus (ECN) from the neck muscles splenius (SP) and biventer cervicis (BC) was examined electrophysiologically. These muscles are divided into a number of serially arranged compartments and are supplied by nerves from different cervical segments. About one-third of ECN neurons receive input from a single nerve. The majority of ECN neurons, however, receive input from more than one nerve in each muscle. ECN neurons are also limited in their ability to follow high frequency nerve stimulation and they frequently exhibit non-linear following. The connections and characteristics of ECN neurons suggest that a minority of neurons in the nucleus have the potential for the faithful transmission of afferent signals, but the majority have the potential to transform incoming patterns of muscle receptor discharge.
Afferent Pathways↗
Branching structure of motoneuron stem dendrites: a study of neck muscle motoneurons intracellularly stained with horseradish peroxidase in the cat.
The branching structure of the stem dendrites of five motoneurons innervating the dorsal neck muscles, biventer cervicis and complexus, was examined in the adult cat using intracellular staining techniques. The dendritic tree of each motoneuron was reconstructed completely and then dissected into several parts, each corresponding to the branches. Twenty-five of the 49 stem dendrites examined had branches which confined to a small region of the territory occupied by the complete dendritic tree. These dendrites were distributed to one of three zones, a ventral zone deep in the ventral horn, a lateral zone dorsolateral to the motor nucleus, and a medial zone dorsomedial to the motor nucleus. The remaining stem dendrites projected to two or more of these zones and occasionally occupied a region almost as large as the territory occupied by the complete dendritic tree. The frequency of each type of stem dendrite, defined according to the number and location of the zones to which they projected, was remarkably consistent from motoneuron to motoneuron. The maximum order of branching reached by stem dendrites of biventer cervicis and complexus motoneurons was variable. Stem dendrites whose maximum order of branching was four or less usually had one major stalk from which emerged simple, unbranched, side processes. The branching structure was not related, in a simple manner, to the dendritic distribution pattern. These results indicate that the distribution and branching structure of motoneuron stem dendrites are organized in a complex, but precise, fashion which could play an important role in the integrative properties of the motoneuron.
Animals↗
Visual responses on neck muscles reveal selective gating that prevents express saccades.
Express saccades promote the acquisition of visual targets at extremely short reaction times. Because of the head's considerable inertia, it is unknown whether express saccades are accompanied by a parallel command to the head. Here, by recording electromyographic (EMG) activity from monkey neck muscles, we demonstrate that visual target presentation elicits time-locked, lateralized recruitment of neck muscles at extremely short latencies (55-95 ms). Remarkably, such recruitment not only accompanies express saccades, but also precedes nonexpress saccades, occasionally by up to 150 ms. These results demonstrate selective gating of components of descending commands from the superior colliculus to prevent express saccades yet permit recruitment of a head orienting synergy. We conclude that such selective gating aids eye-head coordination by permitting force development at neck muscles while a decision to commit to a gaze shift is being made, optimizing the contribution of the more inertial head to the ensuing gaze shift.
Animals↗
Contralateral, midline, and commissural motoneurons of neck muscles: a retrograde HRP study in the cat.
Retrograde transport of HRP has been used to examine the distribution of motoneurons supplying the dorsal neck muscles biventer cervicis, and complexus in the cat. Retrogradely filled cells were present in the expected sites in lamina IX of the ventral horn, but were not confined to that area. Retrogradely labelled cells were also found more dorsally in the ventral horn and in the white matter medial to the ventral horn. Other filled cells were found in the commissural nuclei and in laminae VII and VIII contralateral to the nerve being dipped. Cells in the ipsilateral lamina IX ranged in size from 15 to 70 microns. Cells lying outside this region were smaller with the majority having mean equivalent diameters, of 40 microns or less.
Animals↗
[Distribution of motor nuclei in feline ventral neck muscles].
The distribution of motor nuclei in feline neck muscles at the level of the third and fourth cervical vertebrae of spinal cord was investigated, using retrograde labelling with horseradish peroxidase (HRP). HRP powder was directly injected into the cut ends of the peripheral nerves innervating each muscle. Investigated muscles in this thesis included 5 ventral muscles: Levator scapulae m.(LS), Levator scapulae ventralis m.(LSV), Longus colli m.(LC), Longus capitis m. (LCP), Intertransversarius ventralis m.(ITV). Two dorsal muscles were also examined; Splenius m.(SP) and Biventer m.(BV). The findings in retrogradely labelled motoneurons of each muscle were as follows: 1) LS and LSV (V1 ventral muscles) Labelled motoneurons were observed at the lateral border of the ventral horn, and the distribution of LSV was more dorsal than that of LS. Their cellular distributions varied from the rostral end of the third cervical segment dorsolaterally to the caudal end of the fourth cervical segment ventromedially. 2) LC, LCP and ITV (V2 ventral muscles) Labelled motoneurons were observed at the medial border of the ventral horn. The distribution of LCP was more dorsal than that of LC and ITV, but their cellular distributions were largely intermingled. The variation in cellular distribution, which was observed in V1 ventral muscles, was not recognized in this muscle group. 3) SP and BV (D1 and D2 dorsal muscles) Labelled motoneurons were observed at the apex of the ventral horn, referred to as the ventromedial nucleus by Rexed. The distribution of SP was more dorsolateral than that of BV, and the changes in cellular distribution seen in V1 ventral muscles were also observed in these muscles. Some unorganized labelled cells were found at the medial border of the ipsilateral ventral horn, anterior funiculus, anterior commissure and contralateral ventral horn. These irregularly positioned cells were not found in the staining of the ventral muscles. Organized distributions of motoneurons in the ventral horn corresponded respectively to the classification of trunk muscles, as described by Nishi (1938) in accordance with the peripheral innervation of each trunk muscle. These results indicate that the pattern of peripheral innervation reflects the spinal level, and provides important information for electrophysiological analysis of the neural network between the central and peripheral nervous systems.
Animals↗
Neck muscle responses to stimulation of monkey superior colliculus. I. Topography and manipulation of stimulation parameters.
The role of the primate superior colliculus (SC) in orienting head movements was studied by recording electromyographic (EMG) activity from multiple neck muscles following electrical stimulation of the SC. Combining SC stimulation with neck EMG recordings provides an objective and sensitive measure of the SC drive onto neck muscle motoneurons, particularly in relation to evoked gaze shifts. In this paper, we address how neck EMG responses to SC stimulation in head-restrained monkeys depend on the rostrocaudal, mediolateral, and dorsoventral location of the stimulating electrode within the SC and vary with manipulations of the eye position prior to stimulation onset and changes in stimulation current and duration. Stimulation predominantly evoked EMG responses on the muscles obliquus capitis inferior, rectus capitis posterior major, and splenius capitis. These responses became larger in magnitude and shorter in onset latency for progressively more caudal stimulation locations, consistent with turning the head. However, evoked responses persisted even for more rostral stimulation locations usually not associated with head movements. Manipulating initial eye position revealed that the magnitude of evoked responses became stronger as the eyes attained positions contralateral to the side of stimulation, consistent with a summation between a generic command evoked by SC stimulation and the influence of eye position on tonic neck EMG. Manipulating stimulation current and duration revealed that the relationship between gaze shifts and evoked EMG responses is not obligatory: short-duration (<20 ms) or low-current stimulation evoked neck EMG responses in the absence of gaze shifts. However, long-duration stimulation (>150 ms) occasionally revealed a transient neck EMG response aligned on the onset of sequential gaze shifts. We conclude that the SC drive to neck muscle motoneurons is far more widespread than traditionally supposed and is relayed through intervening elements which may or may not be activated in association with gaze shifts.
Animals↗
Influence of neck muscles on mouth pressure response to cervical magnetic stimulation.
Measurement of mouth pressure (Pm) in response to electrical phrenic nerve stimulation (Es) provides a simple noninvasive means to assess diaphragm function. An even simpler measure would be to use the Pm twitch response (Pm,t) to cervical magnetic stimulation (CMS) rather than to Es. Because CMS coactivates the diaphragm and inspiratory neck muscles (INM), CMS-Pm,t accurately reflects diaphragm function only if the corresponding INM contraction does not produce inspiratory pressures by itself. In patients with recent-onset bilateral diaphragm paralysis, it has been demonstrated that CMS-Pm,t was indeed zero; however, INM hypertrophy could change this situation and lead CMS-Pm,t to overestimate the performance of the diaphragm. To address this issue, we studied nine patients with amyotrophic lateral sclerosis (ALS) who had evidence of diaphragmatic paralysis and compensatory hypertrophy and hyperactivity of inspiratory neck muscles. The response to CMS was described in terms of diaphragm electromyogram (EMG), Pm, and abdominal (AB) and rib cage (RC) motion. No EMG response to CMS could be observed in most cases, and CMS was always associated with AB paradox. Nevertheless, a negative Pm,t swing was recorded with an amplitude of -2.6 +/- 1.0 cm H2O (mean +/- SD). We conclude that inspiratory neck muscle hypertrophy can significantly influence the Pm response to CMS. This should be taken into account when using the CMS-Pm combination in patients with possible chronic diaphragm dysfunction.
Aged↗
Three-dimensional isometric strength of neck muscles in humans.
STUDY DESIGN: Three-dimensional moments were measured experimentally during maximum voluntary contractions of neck muscles in humans. OBJECTIVES: To characterize the maximum moments with attention paid to subject size and gender, to calculate moments at different locations in the neck, and to quantify the relative magnitudes of extension, flexion, lateral bending, and axial rotation moments. SUMMARY OF BACKGROUND DATA: Few studies of neck strength have measured moments in directions other than extension, and it is difficult to compare results among studies because moments often are resolved at different locations in the cervical spine. Further, it is not clear how subject size, gender, and neck geometry relate to variations in the moment-generating capacity of neck muscles. METHODS: Maximum moments were measured in 11 men and 5 women with an average age of 31 years (range, 20-42 years). Anatomic landmarks were digitized to resolve moments at different locations in the cervical spine. RESULTS: When moments were resolved about axes through the midpoint of the line between the C7 spinous process and the sternal notch, the maximum moments were as follows: extension (men, 52 +/- 11 Nm; women, 21 +/- 12 Nm), flexion (men, 30 +/- 5 Nm; women, 15 +/- 4 Nm), lateral bending (men, 36 +/- 8 Nm; women, 16 +/- 8 Nm), and axial rotation (men 15 +/- 4; women, 6 +/- 3) Nm). The magnitudes of extension, flexion, and lateral bending moments decreased linearly with vertical distance from the lower cervical spine to the mastoid process. CONCLUSIONS: Moments in three dimensions were quantified with regard to subject size and location along the cervical spine. These data are needed to characterize neck strength for biomechanical analysis of normal and pathologic conditions.
Adult↗
Perceptual and oculomotor effects of neck muscle vibration in vestibular neuritis. Ipsilateral somatosensory substitution of vestibular function.
Afferent cervical somatosensory input may substitute for absent vestibular information as part of central vestibular compensation after unilateral peripheral vestibular deficit. In order to determine the particular contribution of neck muscle spindles to the perception of body orientation and to the oculomotor system, we measured (i) the subjective visual straight ahead (SVA) by psychophysical tests and (ii) the changes in eye position by video-nystagmography during unilateral stimulation of the posterior neck muscles by vibration (100 Hz). Twenty-five patients with subacute unilateral vestibular lesion (vestibular neuritis) and 25 controls participated in the study. Vibration elicited a horizontal displacement of SVA towards the side of stimulation in all subjects. Mean displacement (+/- SD) was 3.28 +/- 2.96 degrees for right-side and 3.45 +/- 2.93 degrees for left-side stimulation in controls. Muscle stimulation on the patients' lesion side induced a significantly higher displacement (11.51 +/- 6.63 degrees) than contralateral stimulation (3.04 +/- 2.95 degrees, P < 0.01, paired Student's t test). The mean difference during stimulation between the two sides in the patients was 8.02 +/- 5.52 degrees; in the controls, however, it was only 0.74 +/- 0.47 degree (P < 0.001, Student's t test). This asymmetry increased gradually in patients over a period of weeks, reaching a maximum at days 60-80 and declining thereafter. Videonystagmography revealed that ipsilateral stimulation in patients induced large horizontal eye deviations of up to 25 degrees towards the side of the lesion (9.1 +/- 7.6 degrees, n = 18). Contralateral stimulation induced only small shifts, which were within the range of controls. The correlation coefficient between displacement of the SVA and change in eye position was high (r = 0.94, P < 0.0001), indicating that the shift of SVA is the perceptual correlate of the directional change of gaze in space. This interpretation was supported by two control experiments in which the subject was required to (i) indicate the subjective straight ahead by finger-pointing with the eyes closed and (ii) adjust SVA when looking through horizontally reversing prisms. Vibration of neck muscles caused almost no displacement of the SVA when it was indicated by pointing with the eyes closed, but reversed the direction of the displacement if the subject wore reversing prisms. In summary, our data showed: (i) an increase in muscle spindle input following unilateral vestibular lesion; (ii) this increase is asymmetrical, restricted to the affected side, and gradually builds up over weeks; and (iii) the perceived effects during vibration are secondary to changes in eye position rather than changes in cortical representation of body orientation. This is the first study to demonstrate a unilateral increase in somatosensory weight, which substitutes for missing vestibular input.
Adolescent↗
Electromyographic activity of neck muscles in patients affected by retrocollis under the influence of stimulation and coagulation of the prestitial nucleus of the midbrain.
In 2 patients with retrocollis, the positive effects obtained by stereotactic high frequency coagulation of the prestitial nucleus on the tonic activity of the neck muscle were studied electromyographically and clinically. Before the stereotactic therapy, electromyographic recordings at rest were recorded from the musculi splenii. During stimulation of the prestitial nucleus at frequencies of 8, 25 and 50 Hz, the EMG activity at rest diminished in frequency and amplitude and ultimately disappeared. Passage from the EMG recordings at rest to electrical silence took place, in one case, though a rhythmic activity of potentials grouped at 11/s. After coagulation of the prestitial nucleus, the involuntary contractions of neck muscles disappeared and electrical silence occurred. On reexamination 1 month later, the positive results were still present.
Electric Stimulation↗
Relationship between sleep, neck muscle activity, and pain in cervical dystonia.
OBJECTIVE: The interactions between sleep, neck muscle activity, and cervical spinal pain were examined in a controlled study with nine patients suffering from idiopathic cervical dystonia (ICD; also referred to as spasmodic torticollis), and nine gender- and age-matched controls. METHODS: From each participant, two all-night polysomnograms with additional electromyographic recordings from the sternocleidomastoid and upper trapezius muscles were obtained. The first night was for habituation to the laboratory environment; the second night for experimental data collection. Visual analogue scales were used to collect intensity and unpleasantness ratings of cervical spinal pain before and after the second sleep recording. RESULTS: None of the standard sleep variables showed statistically significant differences between average values of both groups of participants. However, a significantly larger variance in sleep latency was obtained for the ICD patients. In general, abnormal cervical muscle activity decreased immediately when lying down without the intention to go to sleep. Subsequently, abnormal muscle contractions were gradually abolished in all ICD patients during the transition from relaxed wakefulness to light NREM sleep. Following this transition phase, no more abnormal EMG activity was found in any of our patients. Finally, cervical spinal pain intensity and unpleasantness were reduced by about 50% overnight. CONCLUSIONS: Both supine position and sleep can be associated with an improvement of symptoms of ICD, and this disorder does not induce any sleep perturbations.
Adult↗
Anticipatory neck muscle activity associated with rapid arm movements.
This study reveals the existence of a backward acceleration of the head prior to the onset of voluntary raising movements of the upper limb. This backward acceleration is produced by the displacement of the head-trunk as a whole. The anticipatory head movement is organized according to a sequence of activation and desactivation of the neck muscles, time locked with the anticipatory leg muscle activity. These findings highlight the existence of a complex postural behavior selected in advance of movement. It is proposed that the feedforward type of neural control of neck muscles should not be interpreted as a compensation to postural perturbation. This anticipatory process might play an important role in the widespread postural fixation of the cervical and dorsal spine.
Arm↗
Frontal 'oculomotor' area in alert cat. II. Unit discharges associated with eye movements and neck muscle activity.
(1) Unit activity in front 'oculomotor' cortex was recorded extracellularly from sites where subsequent electrical stimulation, using threshold current (50 microamperes), could elicit both eye movements and simultaneous neck EMG acitivity. (2) Of 103 cells, 19% were related to either eye movements or neck EMG activity. Cells could be grouped into three categories: (a) Directional (D) cells (31%) discharged before and during saccadic eye movements, whenever the eyes followed a target in one specific direction. Spontaneous saccades, or vestibularly driven nystagmus, in either the light or dark, elicited no responses. (b) Conditionally directional (CD) cells (43%) discharged following (i) tracking saccades; (ii) spontaneous saccades and (iii) the quick phase of nystagmus, in all directions. There usually was a slight discharge preference for one given direction, and this preference was enhanced whenever visual tracking was restricted to the preferred direction. One-third of CD cells responded to stimulation of the contralateralal biventer cervicis neck muscle (min lat. 20 msec). (c) Neck EMG (N) cells (26%) discharged in association with, and preceding, changes in neck muscle activity. These cells also responded to stimulation of the contralateral biventer cervicis muscle (min lat. 10 msec). (3) For points in the lateral 'oculomotor' region (as defined by stimulation: see ref. 17), the directions of evoked saccades, and the directions of spontaneous saccades associated with unit discharges, were sililar. In the medial region 17, the directions of evoked saccades were roughly opposite to the directions of spontaneous eye movements favoured by unit discharges.
Action Potentials↗
[Embryogeny of facial, mastication, tongue, palate and neck muscles (author's transl)].
The mesenchymal origin muscular tissues entailing some difficulties in the knowledge of certain muscles embryogeny, two methods are therefore applied: the comparison of the ontogenesis data with those of comparative anatomy and the use as a guide of the functional motor unit with which the muscle combines. In resorting to these methods necessary precautions are precisely defined. The origins of the concerned muscles are, at first, situated among those of the whole musculature subjected to will, which are of two types "somitic" and "branchial". The realities lying under these two misleading terms are analysed. Then the usual data on each of the muscular groups embryogeny reviewed and compared, if necessary, with recent works. For the facial muscles a confusion results from the use of the term platysma both in comparative anatomy and in embryology, in pursuance of transposition, exact on that particular point, of the philogenic development of these muscles in ontogenesis. The development of these muscles comes in the scope of the extensive general character of the superficial hyoïd arch derivatives, and their topographic and functional particularities should be brought together with the disposition of the facial nerve nucleus and its arising fibres. Among the muscles in action in the mastication, a link appears between their precise role in this function and their embryogeny. For the neck muscles, the spinal nerve systematisation and the variations of the sterno-mastoïd muscle in mammals agree in assigning to this muscle an entire somitic origin lying exactly at the junction with the so-called branchial muscles. The somitic origin of the tongue muscles and the sharing between the somitic and branchial origins of those of the soft palate bring to light the place in the organism of these two anatomic structures. Then, the conjunction of muscles proceeding thus from two origins in these anatomic structures carries a particular signification in man by reason of the language.
Anatomy, Comparative↗